Wisbech Co-operative supermarket was closed for nearly an hour earlier this afternoon after smoke was spotted coming from a cooler unit in the town centre store.
Crews from Wisbech and March attended the incident which happened at around 2.50pm. Staff and customers were evacuated.
A fire service spokesman said firefighters had to dismantle the fridge unit in a bid to discover the cause of the smoke, which was found to be an electrical fault.
The store later re-opened.